1. Field of the Invention
This invention relates generally to telecommunications systems having mobile subscribers and, more particularly, to a method and system for managing a subscriber database in a cellular telecommunications system.
2. History of the Prior Art
A universal mobile telephone system (UMTS) is a mobile telephone system in which each subscriber is assigned a unique personal number. A subscriber can be contacted by using the personal number, no matter where the subscriber is located within the system. The personal number is unique for each subscriber and, once assigned, does not change even if the subscriber changes his permanent home location within the system.
Because a UMTS could potentially contain millions of subscribers, the storage and handling of subscriber location information and subscriber data presents problems not found in present day mobile radio systems.
In present day mobile radio systems it is usual to provide one common home location register (HLR) database for a number of mobile switching centers (MSCs) in order to centralize and simplify maintenance. The HLR database contains location information and other records on a large number of subscribers, for example, 100,000 or more subscribers, according to subscriber number, that are assigned the coverage area of the MSCs as a home system. A visitor location register (VLR) is also provided, e.g. one in each MSC. The VLR contains necessary data related to mobile stations not assigned the coverage area of the MSCs as a home system, but that are visiting the coverage area.
When a call is received for a mobile subscriber, the number of the called subscriber is analyzed in the first contacted MSC (anchor MSC). The identity of the HLR database associated with the called subscriber is then determined by consulting a universal fixed table, that is contained in each MSC, associating each subscriber number with a HLR database. The anchor MSC then signals the called subscriber's HLR database and requests and receives from this HLR a roaming number allowing routing of the received call to the visited MSC in which the called subscriber is presently located.
A problem arising with a UMTS is that because of the large number of UMTS subscribers, a translation between a subscriber number and an associated HLR database is not available in a universal fixed table and not available as general information in all MSCs of the UMTS. When a call is made to a subscriber it is necessary then to locate a node somewhere in the network that can translate the called subscriber's number into location information.
Known proposed techniques of location data management for UMTSs are based on rules that have been defined for the general subscriber. One proposed technique of location data management in a UMTS is based on a hierarchical node structure determined by fixed logical relationships defined by a fixed pointer structure within the system. In this type of hierarchical node structure, the pointer structure is distributed throughout the nodes of the system and each subscriber is assigned the identical pointer structure. The pointer structure comprises a number of logical connections or paths between nodes. In the pointer structure, each of the upper level nodes contains a logical connection to at least one of a number of fixed lower level nodes. Location pointers within the pointer structure in the upper level nodes may be set to point to one of the lower level nodes to which it is logically connected, if it is known that the mobile is located in that lower level node or in a node, along a path of logical connections stemming downward from that lower level node in the hierarchical node structure. Upper level nodes cannot be reconfigured to point to a lower level node that is not logically connected to the upper level node in the location pointer structure.
Tracking the location of subscribers in a UMTS involves the task of location updating. In location updating, databases containing information on subscriber's locations within the system are maintained so that a subscriber may be located when necessary, as, for example, when a call directed toward the subscriber is received in the system. Searching is a related resource intensive task in which the system searches for the location of a called subscriber in one or more of the databases distributed throughout the system that contain location information on the called subscriber.
Database maintenance in a UMTS also includes the task of transferring personalized subscriber data from one database to another as a subscriber moves throughout the system. Personalized subscriber data is a particular type of data that should be located in a database of the system area in which the subscriber is currently located, rather than remain in a home database in the subscriber's original home system area.
Location updating and searches in known UMTS systems are performed along paths defined by the fixed location pointer structure. Because the movement behavior of different mobile subscribers using the system varies and location update and searching requirements will vary from subscriber to subscriber, inefficiencies result from the above discussed fixed location pointer structure. With this type of fixed location pointer structure location updating or searching cannot be optimized for the individual subscriber.
A similar problem exists with existing subscriber data management. In known systems, rules that have been defined for the general subscriber are used to determine the division and transferring of data from one database to another. Subscriber data management also cannot be optimized for the individual subscriber's behavior.
In a universal mobile telephone system the resource intensive tasks of location updating, searching and database management may consume a large portion of available system resources. In a system covering a large geographic area and having a large number of subscribers, these tasks could effect system performance and efficiency. Therefore, a need exists for a method and system of optimizing location updating, searching and/or subscriber data management for individual subscribers within a mobile telephone system.